Hygrometer



Sept. 7, 1937.

H. 4G. Ross HYGROMETER Filed Aug. 16, 1935 lPatented Sept. 7, 1937 2 Claims.

My invention relates to the design of a hygrometer for measuring the moisture content of the air. The purpose of my invention is to provide an inexpensive instrument which gives a direct numerical reading of percent relative humidity without calculation, use ot charts, or interpolation of curves, and still employs the accurate wet and dry bulb type of measurement. This is accomplished by adding tothe regular type of wet and dry bulb hygrometer, a simple mechanical arrangement which makes it direct reading.

The objects and advantages of the invention will be apparent from the following specification.

In the drawing illustrating preferred forms of my invention:

Figure 1 shows my preferred form wherein two sliding members are used for setting opposite the thermometer levels;

Figure 2 shows a partly cut-away side view of the instrument as shown in Figure l.

Referring more particularly to the drawing, I is the frame or body of the instrument, 2 and 3 are similar thermometer tubes, i5 is a water container held by clip It and feeding water through wick Il to keep bulb of thermometer 2 wet. il and 5 are the scales of the thermometers being similar and graduated in degrees Fahrenheit. The part thus far described is common to all wet and dry bulb hygrometers.

In the preferred form of my invention I employ two slots 6 and 'I in which are mounted two sliding members 8 and 9. These members can be slid the full extent of their respective slots and the small pointer on the side of each member is to be placed opposite the level of the liquid in each thermometer tube. The moving plate Ill is mounted on both sliding members being free to rotate about the pin I2 on member 8 and having in it a slot II which slides on and turns about pin I3 of member 9. The extent of the body I is such that the plate is free to slide up and down as the sliding members 8 and 9 move up and down, and it can also rotate about pin i2 as member 9 moves with respect to member t. The

amount which plate l0 may rotate about pin l2 is limited to that required by the eXtreme differential which would occur normally between the two thermometer readings.

On the plate l are a number of figures representing different values of percent relative humidity, These are arranged in such position that the correct one appears in the aperture I4 for any given setting of the two sliding members 8 and 9. To insure the iigure being centered in aperture M, the edges of slots 5 and l may be notched,

or a rectangular frame may be placed around 5 each figure as shown at 25.

It is obvious that I might derive the same result by having the plate it pivot about pin I3 and have a Slot to Slide on pin l2, or that the plate Ill project downwardly instead of upwardly in 10 which case the aperture Ill would be near the bottom of the instrument.

From the foregoing description taken in connection with the accompanying drawing, it will be manifest that a hygrometer of the wet and 15 dry bulb type is provided which will give direct numerical reading of percent relative humidity but, as many changes could be made in the above description and many apparently widely different embodiments of the invention may be constructed 20 within the scope of the appended claims without departing from the spirit or scope thereof, it is intended that all matters contained in the said accompanying specification and drawing shall be interpreted as illustrative and not in a limitative 25 or restrictive sense.

Having thus described the invention, what I claim as new and desire to secure by Letters Patent is:-

1. In a hygrometer, a frame, two thermometer 30 tubes, means for keeping the bulb of one tube wet, an aperture in said frame, slots in said frame parallel to each tube, a member slidably mounted in each slot, a plate adjustably attached to both slidable members so that it is capable of move- 35 ment parallel to the slots or of orientation about either member as centre, numeric values of percent relative humidity printed on the plate in such position that the proper one shows through said aperture when the slidably mounted members 40 are set opposite the thermometer levels.

2. In a hygrometer, a frame, two thermometer tubes, means for keeping the bulb of one tube wet; slots in said frame paralleling said tubes, an aperture in said frame, a movable indicia bearing 45 plate behind said frame, and indicators rotatably connected with said plate and sliding in said slots which when set opposite thermometer levels gives direct reading of said indicia indicating percent relative humidity through said aperture. 50

HUGH G. ROSS. 

